Ditch Witch produced the J20 from the late 1980s to the early 2000s. Look for the stamped serial number on the left frame rail near the wheel. If it's gone, look at the hydraulic pump brand (Eaton vs. Sundstrand) and the engine model. You may need the "Universal J20 Supplement" manual that covers all variations.
Check the open transmission under the plate where the gear shifter is located; remove the cover to oil the internal components. Dig Chain Gearbox
: You can often find physical "Owner & Parts Manuals" from the 1960s and 70s on Key Mechanical Components & Maintenance Experts and long-term owners from TractorByNet highlight several critical areas for J20 upkeep: Rear Gear Box
